object

var Builtins = []struct {
	Name    string
	Builtin *Builtin
}{
	{
		"len",
		&Builtin{Fn: func(args ...Object) Object {
			if len(args) != 1 {
				return newError("wrong number of arguments. got=%d, want=1", len(args))
			}
			switch arg := args[0].(type) {
			case *Array:
				return &Integer{Value: int64(len(arg.Elements))}
			case *String:
				return &Integer{Value: int64(len(arg.Value))}
			default:
				return newError("argument to `len` not supported, got %s", args[0].Type())
			}
		}},
	},
	{
		"puts",
		&Builtin{Fn: func(args ...Object) Object {
			for _, arg := range args {
				fmt.Println(arg.Inspect())
			}
			return nil
		}},
	},
	{
		"first",
		&Builtin{Fn: func(args ...Object) Object {
			if len(args) != 1 {
				return newError("wrong number of arguments. got=%d, want=1", len(args))
			}
			if args[0].Type() != ARRAY_OBJ {
				return newError("argument to `first` must be ARRAY, got %s", args[0].Type())
			}
			arr := args[0].(*Array)
			if len(arr.Elements) > 0 {
				return arr.Elements[0]
			}
			return nil
		}},
	},
	{
		"last",
		&Builtin{Fn: func(args ...Object) Object {
			if len(args) != 1 {
				return newError("wrong number of arguments. got=%d, want=1", len(args))
			}
			if args[0].Type() != ARRAY_OBJ {
				return newError("argument to `last` must be ARRAY, got %s", args[0].Type())
			}
			arr := args[0].(*Array)
			length := len(arr.Elements)
			if length > 0 {
				return arr.Elements[length-1]
			}
			return nil
		}},
	},
	{
		"rest",
		&Builtin{Fn: func(args ...Object) Object {
			if len(args) != 1 {
				return newError("wrong number of arguments. got=%d, want=1", len(args))
			}
			if args[0].Type() != ARRAY_OBJ {
				return newError("argument to `rest` must be ARRAY, got %s", args[0].Type())
			}
			arr := args[0].(*Array)
			length := len(arr.Elements)
			if length > 0 {
				newElements := make([]Object, length-1, length-1)
				copy(newElements, arr.Elements[1:length])
				return &Array{Elements: newElements}
			}
			return nil
		}},
	},
	{
		"push",
		&Builtin{Fn: func(args ...Object) Object {
			if len(args) != 2 {
				return newError("wrong number of arguments. got=%d, want=2", len(args))
			}
			if args[0].Type() != ARRAY_OBJ {
				return newError("argument to `push` must be ARRAY, got %s", args[0].Type())
			}
			arr := args[0].(*Array)
			length := len(arr.Elements)
			newElements := make([]Object, length+1, length+1)
			copy(newElements, arr.Elements)
			newElements[length] = args[1]
			return &Array{Elements: newElements}
		}},
	},
}